Road surface characterization using near infrared spectroscopy

Sammanfattning: This thesis presents a technology and method for classifying and characterizing different road conditions such as dry asphalt and asphalt covered with water, ice and snow. The method uses light sources of different wavelengths to illuminate the road surface and a detector to measure the reflected light from the road surfaces, dependent on how the surface have absorbed, scattered and polarized the light it is possible to classify the road condition. However, knowing what substrate that is on the asphalt is not enough to make good road grip estimations. Hence, by applying a radiative transfer model and estimate parameters such as the porosity, roughness and depth of the substrate it is possible to get more information that could improve a road grip estimate. Such investigations were carried out both in a laboratory environment and on actual roads. The technology here presented shows potential for classifying and characterizing different road conditions. Statistics shows that many traffic accidents with fatal outcome can be related to slippery road conditions. The most hazardous road conditions are the ones that are hard for the driver to detect and that appears sudden on the road. A sensor that can classify road conditions, could improve road safety considerably. Road condition information could be used in several applications, such as in the own vehicle both to inform the driver and safety applications such as the electronic stability program (ESP), anti-lock brake system (ABS) or the traction control system (TCS) on the prevailing road conditions. Such information could also be sent to other drivers and to the infrastructure, making it possible to plan a travel route depending on the prevailing road conditions. Or as information to road maintenance so they know where work is needed. Since there are a number of prototypes and ideas how to estimate the road grip, it is important that different methods are evaluated and tested in the same way. Hence, this thesis includes test methods and metrics to verify the various systems and investigate the weaknesses and strengths of the technologies. This is also carried out for the technology presented in this thesis.